Commitments and Contingencies (Schedule of Environmental Loss Contingencies) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	$ 79
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	97	$ 79
Provisions/adjustments	4	34
Cash reductions	(4)	(8)
Ending balance	97	105
Duke Energy Carolinas [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	25
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	11
Provisions/adjustments	0	(1)
Ending balance	10	10
Progress Energy [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	4
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	17	27
Provisions/adjustments	3	4
Cash reductions	(2)	(6)
Ending balance	18	25
Duke Energy Progress [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	1
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5	8
Provisions/adjustments	0	3
Cash reductions	(1)	(4)
Ending balance	4	7
Duke Energy Florida [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	3
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	12	19
Provisions/adjustments	3	1
Cash reductions	(1)	(2)
Ending balance	14	18
Duke Energy Ohio [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	43
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	54	27
Provisions/adjustments	1	28
Cash reductions	(1)	(1)
Ending balance	54	54
Duke Energy Indiana [Member]
Environmental Matters Details [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss	7
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10	7
Provisions/adjustments	3	3
Cash reductions	(1)	(1)
Ending balance	$ 12	$ 9